Open .htaccess and set: SetEnv MAGE_IS_DEVELOPER_MODE “true” at the end of the file

Open .htaccess and set: php_value display_errors On somewhere within <IfModule mod_php5.c>

Rename /errors/local.xml.sample to /errors/local.xml

Create one sample customer with full valid American address (for example use US/California, city Alamo with ZIP 94507), and one with full valid non American address (other country) to test payment and shipping gateways properly

Compensate for the possible lack of email server by doing something like explained in this article.